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In 1995 McArthur Wheeler robbed two banks with lemon juice on his face believing it would make him invisible to security cameras like invisible ink. He even smiled at the cameras and was caught within hours. His case inspired the research that led to the discovery of the Dunning Kruger effect.
In the spring of 1995, McArthur Wheeler walked into two banks in Pittsburgh, Pennsylvania, to carry out robberies. What made the case unusual wasn’t the crime itself but his belief in a bizarre “getaway tactic.” Wheeler had smeared lemon juice on his face, convinced it would render him invisible to security cameras. His reasoning came from the fact that lemon juice can be used as invisible ink, only becoming visible when exposed to heat. He mistakenly assumed the same principle applied to surveillance footage.
When police reviewed the tapes, Wheeler was easily identifiable, he even looked directly at the cameras and smiled, confident in his “invisibility.” Within hours, police arrested him. Shocked at being caught, Wheeler reportedly exclaimed: “But I wore the juice!”
The case caught the attention of psychologists David Dunning and Justin Kruger. They were fascinated not just by Wheeler’s flawed logic but by his absolute confidence in it. This became the foundation for their groundbreaking research into cognitive bias. In 1999, they published their study on what is now called the Dunning-Kruger effect: a psychological phenomenon where people with limited knowledge or skill greatly overestimate their competence.
Wheeler’s lemon-juice blunder has since become a textbook example of this effect. It demonstrates how ignorance isn’t simply the absence of knowledge, it can foster misplaced certainty. His case, though humorous in hindsight, underscores a universal human flaw: the less we know, the more likely we are to overestimate our abilities.
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